Interview

The Complete Guide to GitHub Actions Interview Questions

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GitHub Actions has become an essential DevOps tool that every developer should know in 2023 This continuous integration and deployment (CI/CD) tool allows you to automate your development workflows right within your GitHub repositories

In this comprehensive guide, I’ll be covering some of the most commonly asked GitHub Actions interview questions and sample answers you can use to ace your next tech interview. Whether you’re prepping for your dream job or brushing up on your skills, this guide has got you covered!

Why Learn GitHub Actions?

Before jumping into the questions, let’s first go over why GitHub Actions is such a big deal. Here are some key benefits of using GitHub Actions:

  • Automates your development lifecycle workflows including build, test, package, release and deployment.
  • Integrates seamlessly with GitHub – just define YAML workflow files in your repo to get started.
  • Trigger workflows on various events like push, pull requests, issue comments etc.
  • Run jobs on Linux, Windows and macOS environments.
  • Reuse workflows and actions shared on GitHub Marketplace.
  • Matrix builds allow parallel testing across multiple versions.
  • Built-in secrets management for handling sensitive data.

By leveraging GitHub Actions for CI/CD you can streamline release cycles reduce manual errors, and ensure only tested code ends up in production. No wonder it has quickly become a must-have skill!

Frequently Asked GitHub Actions Interview Questions

Here are some of the most common GitHub Actions interview questions that you should prepare for:

Q1. What are the benefits of using GitHub Actions?

Some key advantages of using GitHub Actions are:

  • Automates Continuous Integration and Continuous Deployment (CI/CD) workflows.
  • Easy integration with GitHub – just add YAML files to your repository.
  • Eliminates the need for external CI/CD platforms.
  • Enables testing across multiple environments using matrix builds.
  • Provides flexible self-hosted and cloud-based runners.
  • Includes built-in secrets management for security.
  • Reusable actions available on GitHub Marketplace speeds up builds.
  • Cloud-based model reduces infrastructure costs.
  • Visual interface to track workflow runs and logs.

Q2. How do you define a workflow in GitHub Actions?

Workflows in GitHub Actions are defined as YAML files inside the .github/workflows directory in a repository. A workflow file consists of the following sections:

  • name – Name of the workflow
  • on – Events that trigger the workflow e.g. push, pull_request
  • jobs – One or more jobs that run in parallel
  • steps – Tasks executed within each job

For example:

yaml

name: CIon:   push:    branches:      - master      jobs:  build:    runs-on: ubuntu-latest        steps:    - uses: actions/checkout@v2    - run: make build

This defines a workflow named CI that will run whenever code is pushed to the master branch. It contains one job called build that checks out code and runs the make build command.

Q3. How are secrets handled in GitHub Actions?

Secrets allow you to store sensitive data like API tokens, credentials etc. within GitHub. They are encrypted and only exposed to workflows as environment variables.

To use secrets:

  • Define secrets in your repository settings under the secrets configuration page.
  • Reference the secret as ${{ secrets.secret_name }} in your YAML file.
  • Limit access to secrets by specifying required contexts.

Best practices when using secrets:

  • Avoid exposing secrets in logs or hardcoding in scripts.
  • Regularly rotate secrets to reduce risk of compromise.
  • Revoke secrets immediately if you suspect they have been exposed.

Q4. What are the different GitHub Actions events that can trigger workflows?

Some common GitHub Actions events that can be used to trigger workflows are:

  • push – Run workflow when code is pushed to the repository.
  • pull_request – Execute workflow on PR creation, updates or merging.
  • release – Trigger workflow when a release is published.
  • issue_comment – Run on issue comment events.
  • schedule – Trigger workflow on a cron schedule.
  • workflow_dispatch – Manually trigger workflow through UI or API.

For example:

yaml

on:  schedule:    - cron: '0 12 * * Fri'  # Execute every Friday at 12 PM UTC

This schedules the workflow to run every Friday at noon UTC.

Q5. How can you reuse workflows in GitHub Actions?

There are two ways to reuse existing workflows in GitHub Actions:

1. YAML anchors

Anchor important sections in a YAML file and reference them using aliases:

yaml

jobs:  build:    runs-on: ubuntu-latest    ...    steps:      - &install        run: |          npm ci      - *install           # Reuses install step

2. Import common workflow

Keep reusable workflows in separate files and import them:

yaml

jobs:  build:    uses: ./.github/workflows/common.yml@main

This allows sharing steps between multiple workflows.

Q6. How do you use Docker containers in GitHub Actions?

To use Docker containers in workflows:

  1. Specify docker://image:tag in the runs-on section of the job. This will pull the image from DockerHub.

  2. Use Docker commands like build, push etc. in your workflow steps:

yaml

jobs:  build:    runs-on: docker://alpine:3.5        steps:    - run: docker build . -t myimage    - run: docker push myimage

  1. For private repositories, use docker://ghcr.io/owner/image instead of DockerHub.

  2. Setup Docker login before pushing images:

yaml

    - name: Docker login      run: |        echo "${{ secrets.DOCKER_PASSWORD }}" |         docker login -u "${{ secrets.DOCKER_USER }}" --password-stdin

Q7. What are self-hosted runners in GitHub Actions?

Self-hosted runners allow you to run workflows on your own machines instead of using GitHub’s cloud-based servers. They are useful in cases where you need:

  • More control over hardware, OS, software.
  • Runs requiring GPU, CUDA etc.
  • Data privacy and regulatory requirements.
  • Faster runs if GitHub-hosted runners are busy.

To use self-hosted runners:

  1. Install and register a self-hosted runner agent on your machine.
  2. Specify runs-on: self-hosted in your GitHub Actions workflow.
  3. The job will execute on your self-hosted machine.

Maintenance of these runners is needed for security, updates and scaling.

Q8. Explain how matrix builds work in GitHub Actions.

Matrix builds allow running workflow jobs across multiple configurations defined in a build matrix. This is useful for testing code across different platforms, languages, or parameters.

To use a matrix build:

  1. Define a strategy section within the job.

  2. Specify a matrix parameter under strategy and provide an array of configurations.

For example:

yaml

strategy:  matrix:    node: [12, 14]    os: [ubuntu-latest, windows-latest]    jobs:  build:    runs-on: ${{ matrix.os }}    steps:    - uses: actions/setup-node@v1      with:        node-version: ${{ matrix.node }}

This will trigger 2 jobs – one running on each OS and node version combination.

Q9. How can you cache dependencies and build outputs in GitHub Actions?

Caching allows you to reuse previously built artifacts, dependencies etc. from previous runs instead of rebuilding them each time. This speeds up workflows significantly.

To cache files/directories:

  1. Use the cache action after checkout:
yaml

    - uses: actions/cache@v2      with:        path: ~/cache        key: ${{ runner.os }}-${{ hashFiles('**/lockfiles') }}

  1. Restore cache if a match is found based on the key provided.

  2. Save any new cache at the end of the job.

The cache key should include inputs that change the cache contents like lock files, branch name etc.

Q10. What are some best practices for writing GitHub Actions workflow files?

Some best practices for writing GitHub Actions workflow files:

  • Keep workflow files small and focused on a single task.
  • Reuse actions and workflows using anchors and imports.
  • Make use of matrix builds for parallel testing.
  • Ensure idempotency so workflows can safely rerun.
  • Use cache directives for faster runs.
  • Follow least privilege principles while using secrets.
  • Add error handling, notifications and rollback logic.
  • Monitor workflow runs on

Submit an interview question

Questions and answers sent in will be looked over and edited by Toptal, LLC, and may or may not be posted, at their sole discretion.

Toptal sourced essential questions that the best GitHub developers and engineers can answer. Driven from our community, we encourage experts to submit questions and offer feedback.

github actions interview questions

[Developer Leadership] Which branches can be made the main branch in a repository? What makes the main branch unique? How do you keep the branches in a repository clean?

By default, master is the main branch. Historically, the gh-pages branch was also treated specially, but not any more.

Any branch can be made the main branch in a repository. Only the fact that it is the default branch that is checked out when a repository is copied makes it unique. It is also the default branch that pull requests will be sent to.

In order to keep branches neat, you can delete the ones that have been fully merged into the main branch on the Branches settings page. 2 .

When merging a pull request on GitHub, you can do one of three things: make a merge commit, squash and merge, or rebase and merge. When might you want to use each?.

Using the Squash and merge option is a good way to preserve a tidy main branch history. Atomic commits are helpful when adding a feature or fixing a bug, but they aren’t always needed when adding the finished work to the main branch. But Squash and Merge should really only be used when the work being pulled together makes a whole.

For a clean commit history, the Rebase and merge option is also useful. This is because some maintainers want to keep the atomic commits that were made while building a feature, but they don’t like the way merge commits look or are noisy. When you do a Rebase and merge, however, it might not be easy to add any new work from the feature branch. If there are any problems with the merged code, this might not be a big deal—just start a new feature bug-fix branch.

When in doubt, Create a merge commit is always a fine, safe option. Some people may think it’s unnecessary to make an extra commit, but the atomic commits and their hashes will be kept from the branch. 3 .

[Operations] What does a command-line script need to do something for a user (do something like g. 2) to clone a repository as part of a continuous deployment task) when two-factor authentication is used to protect the user’s account?

You can use a personal access token. You should use a unique, well-documented token for each script so that they can be revoked and regenerated separately, if necessary.

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GitHub has a lot of tools that can be connected to it, but let’s say you wanted to keep track of every new commit that a developer made to your repository in your own way. How would you go about that?.

GitHub provides APIs with REST and GraphQL layouts.

The need in this question could be met simply by polling either of those APIs, but a proper implementation should use GitHub’s webhooks to trigger an action at some endpoint in your system. 5 .

You don’t have to enter your username and password every time you push a commit to GitHub when you use the repository’s SSH URL. How does GitHub know that it’s you?.

There are two parts to this:

  • Everyone who uses GitHub will be able to see the private key that is linked to your account.
  • GitHub uses the email address of the commit, which can be set for a single repository or for all repositories on a machine.

    • 6 .

[Development/Operations] What are some benefits and limitations of hosting an application using GitHub Pages?

Some benefits are:

  • It’s free!
  • Quick and easy to set up.
  • Service is stable and responsive.
  • It has broad (but not unlimited) licenses that make it great for open-source, non-profit, or prototype projects.

Limitations include:

  • No server-side computation. (This is a limitation, but it’s not a strict downside because it keeps your truly static assets separate from other assets that change.) ).
  • No control over caching, authorization, or any other HTTP headers
  • the software has some soft limitations that could make it unusable for business uses

    • 7 .

What are the possible answers a code reviewer could give? For each answer, describe when a reviewer would use it.

The options are Accept, Comment, or Request Changes. The way these options are used is specific to an organization’s agreed-upon procedures, but generally speaking:

  • Comment is for when we need to talk more or there isn’t a clear winner. It’s there to leave unresolved feedback.
  • Accept means that changes don’t need to be made or are small enough that they don’t need to be looked over again.
  • Request Changes usually means that changes need to be made to the commit before it can be accepted, and the review needs to be sent again after those changes are made.

When it comes to project management, you can use GitHub in a number of ways to keep clients interested.

Say you are starting a project using Agile methodology. You intend to do work in iterations with regular client feedback sessions. What GitHub tools could you use, and how would you explain to your client what they’re for?

There are a range of answers that could be provided here, but the answer should definitely mention issues. Issues are for more than bug reports. Developers can use issues to track and share progress on individual units of work. Discussion on those units can happen asynchronously within the issues as well. The client should know that the work will be defined in these areas and what is expected of them in terms of communication in these areas.

Additionally, the answer could mention the strengths and weaknesses of each of the projects and milestones features.

The work that needs to be done in a certain iteration can be planned out and ranked using a project. This can be done across repositories!

A milestone can be used to group and prioritize related issues within a given repository. One benefit of milestones is that they let you set due dates, but projects are better for keeping track of issues and organizing them by status. A person being interviewed may also talk about other tools that work with GitHub, like ZenHub, and add features like tracking velocity.

Keep in mind that different project owners have different ideas about whether clients should be able to access the actual internal tools for planning and tracking development or whether there should always be communication tools for project planning that don’t get too technical. That disagreement is okay. The purpose of this question is to both get the person to think about it and to find out how they feel about it. 9 .

[Project Management] You are starting a project where you want to keep the code private. Organizational accounts are free for open source projects, while private repositories for personal accounts are free. For many projects, it is sufficient to start with a private personal repository. When or why might you want to migrate to a paid organizational account?.

The main reasons are around team size or administrative flexibility. You can have collaborators on your personal private repositories, but only up to a certain number of collaborators.

Beyond that amount, you have to upgrade your account. However, a personal account upgraded to have unlimited collaborators is still cheaper than an organizational account.

One of the best things about having an organizational account is that you can finetune who can access your repositories and how safe your account is.

It’s also important that you can divide up the work of managing the repository; in personal repositories, only the owner can change the settings. Organizations can be configured for other team members to be administrators as well. 10 .

[Development] What are some steps you can take to ensure the security of your GitHub account?

There are several ways to go about this, but the best ones will all at least mention setting up two-factor authentication (2FA). The candidate may also note that 2FA can be configured as a requirement for organizational collaborators as well.

Other things that may be mentioned are:

  • Getting rid of unused key pairs for your account
  • Making sure that computers that have a key pair to your account are safe
  • Cutting down on the number of access tokens and deploy keys linked to your account and reviewing them often

GitHub has a number of recommendations as well. 11 .

How would you close an issue from a commit? What else could you use an issue from a commit for?

Mention Closes #. anywhere in the commit message, where . is replaced by the issue number within the repository. If the issue is in a different repository than the commit is being made to, use Closes username/repository#. in the commit message.

Any time a user refers to an issue from a commit message, GitHub links to the commit directly from the issue it mentions. Using mentions can be useful as a way of building an easily traversable “paper trail” of related or affected commits. 12 .

What are some of the ways that the GitHub Flow branching pattern is different from the Git Flow branching pattern? How does GitHub make the GitHub Flow branching pattern possible?

Any number of answers could be given, but here are a few that should probably be brought up:

  • There could be a lot of work in progress at any given time that hasn’t been approved for production in Git Flow because it is organized around releases. GitHub Flow, on the other hand, thinks that the main branch is always ready to be deployed.
  • There is not a clear line between your main branch and your development branch in GitHub Flow. Because a hotfix branch is just another branch off of main, this gets rid of the need for things like hotfixes.
  • No matter what branching pattern you use, you should follow good development practices like code review and automated testing. These are especially important when using GitHub Flow. This is because they make people more sure that a certain change won’t mess up the production branch. In two ways, GitHub helps developers follow these best practices: it makes branching and pull request discussions easy and clear for everyone involved in the project, and it adds tools for continuous integration to pull requests.
  • If you use GitHub, you don’t have to use the GitHub Flow workflow. You can also use Git Flow or any other branching workflow.

    • 13 .

[Project Management] You are working on a project that is split across a few private repositories. Some parts of the project are being given to a consulting firm with a few engineers who will need to be able to access the project’s repositories. How would you manage access for those engineers while preserving the privacy of the rest of your repositories?.

You can add collaborators from outside of your organization directly to a repository.

However, it may be better to create teams, as you can administer membership in teams separately from team repository access. Team members are added as members of your organization, so it is important to think carefully about access privileges across the organization overall. For example, in the Member privileges settings, you may want to change the base permissions for an organization member to None, and then add relevant teams to each repository as needed. 14 .

[Leading developers or managing projects] What feature does GitHub offer to make sure that only good issues are added to your repositories?

Github provides issue templates for repository or organization managers to lay out a specific structure that should be followed when someone submits an issue.

Other things that may help:

But sometimes nothing works better than having someone who knows the project and how things are done walk a new contributor through the steps.

There is more to interviewing than tricky technical questions, so these are intended merely as a guide. Not every good candidate for the job will be able to answer all of them, and answering all of them doesn’t mean they are a good candidate. At the end of the day, hiring remains an art, a science — and a lot of work.

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